1. Field of the Invention
The present invention relates to a random number generating device.
2. Description of the Related Art
Random numbers are used to generate keys for encrypting techniques intended for information security. In recent years, in particular, small and fast random number generating devices have been demanded. Pseudo-random numbers are often used to meet this demand.
However, more advanced security techniques have been required for personal information protection or the like. This requires more unpredictable intrinsic random numbers to be generated so as to keep security. Random noise utilizing a physical phenomenon is effective for generating intrinsic random numbers. A known technique for generating random noise on the basis of the physical phenomenon utilizes a fluctuation in diode current. However, amplification of very low white noise requires a large amplifying circuit, making it difficult to obtain a small random number generating device.
A small, fast, and good random number generating device using Si nano-crystal MOSFETs has been proposed (see JP-A 2005-167165 (KOKAI)). In the Si nano-crystal MOSFET, only a very thin tunnel insulating film is interposed between a channel and conductive nano-particles. Thus, thermal fluctuation causes random electron charging and discharging. This randomly varies a current flowing through the channel, resulting in random noise. Converting the random noise into digital random numbers enables the generation of random numbers.
Normal security systems require random numbers to be generated at a rate of at least 1 Mbits/sec. However, the Si nano-crystal MOSFET produces only a low random noise and thus cannot sufficiently generate good random numbers. Further, achieving a random number generation rate of at least 1 Mbits/sec requires a miniaturizing technique which is both technically and economically difficult to implement.
Thus, small, fast, and good random number generating devices have been required in order to further improve information security. However, it has been difficult to provide small high-performance random number generating devices that can sufficiently generate good random numbers.